1. Field of the Invention
The present invention relates to a transistor of a semiconductor device, and more particularly to a transistor structure capable of preventing a direct connection between a metal wiring and a source/drain and a method for fabricating the same.
2. Description of the Prior Art
Where a metal wiring comprised of, for example, an aluminum film is in contact with silicon, the aluminum is generally solved into the silicon. However, the solution of aluminum is non-uniformly generated. Actually, the solution of aluminum is generated at two or three particular points. In other words, a spiking phenomenon occurs that the aluminum penetrates the silicon in the form of a spike. Where a shallow junction is formed at the aluminum/silicon contact region, it may be short-circuited because the aluminum is diffused in the silicon due to the spiking phenomenon.
Referring to FIG. 1, there is illustrated a convention metal oxide semiconductor field effect transistor (MOSFET) and a method for fabricating the MOSFET.
As shown in FIG. 1, the MOSFET has a structure wherein a metal wiring is in contact with source and drain electrodes. For fabricating such a structure, a silicon substrate 1 is prepared which is defined with a P type well and an active region. A channel stop ion implantation region 9 is also defined in the silicon substrate 1. Thereafter, a field oxide film 2, a gate oxide film 3 and a doped polysilicon film 4 are sequentially formed. Thereafter, the resulting structure is subjected to a photolithography process to form a gate electrode. After the formation of gate electrode, source/drain electrodes 7 are forced. A contact hole is then formed. After the formation of contact hole, a metal wiring 8 is formed.
In the conventional MOSFET structure, however, the metal wiring is in direct contact with the silicon substrate such that it comes into contact with the impurity ion-implanted region because the source/drain electrodes are formed after the formation of gate electrode in accordance with the conventional method. As a result, a spiking phenomenon occurs. Due to such a spiking phenomenon, it is difficult to form a shallow junction.